<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p {
            color: red;
        }

        #kk {
            color: #000;
        }

        .aa {
            color: green;
        }
    </style>
</head>

<body>
    <p>这是标签选择器</p>
    <div id="kk">这是id选择器</div>
    <div class="aa">这是class选择器</div>
</body>

</html>